Connecting mechanisms for towed vehicles take a variety of forms, such as clevis and tongue mechanisms, ball and socket mechanisms, pintle hook and ring mechanisms, and the like.
Clevis and tongue mechanisms require a separate pin which is inserted downward through aligned holes in the drawbar and clevis. In contrast ball and socket mechanisms and pintle hook and ring mechanisms comprise only an upward extending lower male hitch member, being the pintle hook or ball, that is attached to the towing vehicle, and a female hitch member, the ring or socket, that is attached to the trailer tongue and drops over and engages the male hitch member make the connection. No separate connecting pin is required. A lock mechanism prevents the male and female members from disengaging.
A typical pintle hook and ring hitch has a base for attachment to the towing vehicle and a hook like lower jaw curving rearward and upward from the base to form the pintle hook, and an upper jaw pivotally attached to base. To connect a towed vehicle, the upper jaw is raised and latched into the open position creating a gap between the top of the pintle hook and the upper jaw. The towing vehicle is moved rearward and the ring on the tongue of the towed vehicle moves through the gap and then the tongue is lowered so that the ring drops over the pintle hook and rests on the bottom of the lower jaw. The upper jaw is then pivoted downward to a closed position where the outer end of the upper jaw is close to the upper end of the pintle hook. The upper jaw closes the gap preventing the ring from disengaging from the pintle hook, and thus locks the ring to the pintle hook.
The upper jaw typically includes a latch mechanism to latch it in either the open or closed positions, and a safety pin is typically required to lock the upper jaw in the closed position in case the latch fails. Such a pintle hook and ring hitch is described for example in U.S. Pat. No. 5,332,250 to Thorwall et al.
In ball and socket hitches the socket mechanism on the trailer tongue typically includes some manner of clamp mechanism that engages the bottom surface of the ball to prevent the socket from moving upward out of engagement with the ball.
U.S. Pat. No. 3,963,266 discloses a combination hitch apparatus with a ball on the lower male hitch member extending up from the lower jaw. The ring on a trailer tongue can drop over the ball to rest on the lower jaw, or a socket on a trailer tongue can drop onto the ball. The upper jaw moves down to closed position where the outer end of the upper jaw is close to the upper end of the ball to close the gap between the upper and lower jaws to prevent a ring from disengaging the lower male hitch member. U.S. Pat. No. 6,139,043 to Gries et al. and U.S. Pat. No. 5,312,128 to Blacklaw, and U.S. Pat. No. 4,844,498 to Kerins et al. also disclose combination hitch apparatus for use with either a ring or socket type trailer tongue.
Canadian Patent Number 2,779,051 to Olson discloses a clevis and tongue hitch mechanism with a drawpin retainer apparatus comprising a retainer key pivotally attached above the drawpin to prevent the drawpin from moving up out of engagement with the hitch.